Process for recovering molybdenum from its ores and concentrates.



F. D. S. ROBERTSON. FOR REOOVERING MOLYBDENUM FROM ITS 0115s AND GONOENTRATES PROCESS 1,118,150

APPLICATION FILED NOV. 14. 1913- Patented Nov.

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2 SH PET F. D. S. ROBERTSON.

I PROCESS FOR REOOVBRING MOLYBDENU M FROM IIS ORBS AND GONGENTRATES.

APPLICATION. FILED NOV. 14, 1913.

1 118 150 Pafunted Nov.

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w/ TN5E5 my yaw T017 I ED STATES PATENT OFFICE.

FREDERICK D. S. ROBERTSON, 0F TORONTO, ONTARIO. CANADA, ASSIGNOR OF THREE- FOURTHS TO MICHAEL J'. OBRIEN, OF RENFREW, ONTARIO, CANADA.

PROCESS FOR RECOVERING MOLYBDENUM FROM ITS ORES AND CONCENTRATES.

To all whom it may concern Be it known that I, FREDERICK Duncan STRUAN ROBERTSON, a subject of the King of Great Britain, and resident of the city of Toronto, in the county of York and Province of Ontario, Dominion of Canada, have invented a new and useful Processfor Recovering Molybdenum from its Ores and Concentrates; and I hereby declare that the following is a full, clear, and exact descripoxid, M00 which melts at a temperature of about 7 90 Cen. This is accomplished by maintaining a temperature of about 800 Cen. with excess of oxygen, according to the reaction I with the formation of fine silky acicular crystals of a very volatile character and readily sublimed. Under these conditions of temperature and atmosphere the tri-oxid of molybdenum, M00 is alone produced, the operation being materially hastened with the addition of steam, thus-:--

The process will therefore be hereinafter described as applied to the production particularly of the tri-oXid of molybdenum from ores or concentrates containing molybdenum by a direct process of volatilizingroasting in a highly oxidizing atmosphere, this being the essential feature of the present invention.

The ores, concentrates, middlings and tailings, containing molybdenum, which will hereafter for convenience be called ores, are crushed, preferably through rolls in order to preserve the flakes and thus eX- pose a greater surface to oxidizing influences, to about eight mesh and introduced to a suitable furnace, mufiie or retort.

The type of apparatus by which the process may be carried into practice is purely Specification of Letters Patent.

Patented Nov. 24, 1914.

Applicaticndiled November 14, 1913 Serial No. 800,981.

arbitrary, but for the purpose of describing the various steps a conventional type of plant is shown in which- Figure 1, is a longitudinal section of a rotary furnace, Fig. 2, is a longitudinal sec ti on of the cooling tower and bag house, Fig. 3 is a cross-section of the furnace, and Fig. l is a broken detail view of the twyered air and steam pipes.

In Fig. 1, a is the roasting cylinder, 6, the ore hopper arranged so as to continuously deliver the ore into the roasting cylinder from which it drops out in its spent condition into the chamber 0, from which it is delivered into the truck d. The fireplace is in the chamber f, which may eitherbe within or at the side of the chamber 0.

Longitudinal ribs a projecting from the lining of the furnace araise the powdered ore as the furnace rotates, and allow it to fall through the heated gases as soon as its angle of repose is exceeded. The fumes and gases pass out at the upper end of the furnace into the cooling chamber 9, and thence through the flue o to the dust tower p, and

bag-house or filter-chamber t, (Fig. 2).

In addition to the air which enters through the firing door of the fire chamber 7, a further supply of air under a pressure of about five pounds per square inch, which has been previously pre-heated by passing through the cooling chamber 9, is maintained by means of the twyered pipe m, the air being moistened by steam which enters through the branched pipe n.

Different degrees of inclination, to suitv different ores and concentrates, can be given to the furnace. During the passage of the fumes through the cooling chamber 9, which may be divided into Water-cooled compartments 9', and is preferably built of solid masonry, considerable condensation takes place, the crystals being withdrawn at intervals through the ports 72.. After their passage through the cooling chamber forty feet long, and about two feet in diameter. These bags may be either open at their lower end and thus connect with casks or bins, or be connected at the bottom in a U-shape. The fine oxid of molybdenum collects inside these bags, while the permanent.

gases, sulfur dioXid, etc, passing through 3 the meshes of the fabric are drawn d the fan 0, and are led into the open stack :0. The waste gases may be recovered to form sulfuric and other compounds, and their heat may be utilized toward raising steam. The charge having thus been introduced into the furnace, the temperature is steadily maintained together with a plentiful oxidizing current, otherwise oxids other than the tri-oxid of molybdenum are apt to be formed and in which case the mass tends to frit and present a frozen appearance. The a'ction of pro-heated air under pressure together with steam and also occasional fresh additions of ore or concentrates will, however, overcome this obstacle. During the roast the charge should present a red, dish appearance and should feel somewhat soft under the rabble, but should not be allowed to become tacky. In order that the charge remain in a more or less pulverulent state and thus permit of a free access of air, it may be necessary to mix with it crushed quartz or sand, but such additions must be carefully added, the character of the ore being taken into account as resulting mixture may react too strongly upon the furnace lining. A similar effect may also be produced, especially in the i longer than; cotton; the bags are usually cleaned or shaken twice in twenty-formv hours. The tri-oxid of molybdenum thus prepared is very pure, and may be further purified, if desired, by similar re-sublimation in a separate similar plant.

Having now particularly described ascertained the nature of the process and the manner of its performance,ll now claim:

1. The direct process for the volatilization and recovery of molybdenum'in the form of pure molybdenum trioxid MoO which consists in subjecting ores containing molybdenum to "a temperature exceeding 790 degrees centigrade in an atmosphere sists in subjecting ores containing molyb- 'denum to a volatilizing temperature, in an atmosphere having an excess of oxygen, Toronto, Ont, November 10th, 1913.

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